Microstructures and mechanical properties of Al 2 O 3 /AZ91 surface nanocomposite layer produced by friction stir processing

In this paper, the effects of friction stir processing (FSP) parameters on the mechanical properties and microstructures of as-cast magnesium AZ91 alloy are investigated. Grain-growth and microhardness of friction-stir-processed specimens with and without nano-sized aluminium oxide (Al 2 O 3 ) particles are compared. The effects of process parameters on tunnelling cavity and other friction stir processing defects are discussed. The paper describes the proper process parameters under which a uniform distribution of nano Al 2 O 3 composite reinforcement with good interfacial integrity and significant grain refinement can be produced. Hardness studies revealed that the incorporation of nano-sized Al 2 O 3 particulates in magnesium matrix caused the SZ hardness to increase.